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02ca144fa4
linux/drivers/char
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Tetsuo Handa c0070e1e60 ttyprintk: Add TTY hangup callback. 
syzbot is reporting hung task due to flood of

  tty_warn(tty, "%s: tty->count = 1 port count = %d\n", __func__,
           port->count);

message [1], for ioctl(TIOCVHANGUP) prevents tty_port_close() from
decrementing port->count due to tty_hung_up_p() == true.

----------
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <unistd.h>

int main(int argc, char *argv[])
{
	int i;
	int fd[10];

	for (i = 0; i < 10; i++)
		fd[i] = open("/dev/ttyprintk", O_WRONLY);
	ioctl(fd[0], TIOCVHANGUP);
	for (i = 0; i < 10; i++)
		close(fd[i]);
	close(open("/dev/ttyprintk", O_WRONLY));
	return 0;
}
----------

When TTY hangup happens, port->count needs to be reset via
"struct tty_operations"->hangup callback.

[1] https://syzkaller.appspot.com/bug?id=39ea6caa479af471183997376dc7e90bc7d64a6a

Reported-by: syzbot <syzbot+43e93968b964e369db0b@syzkaller.appspotmail.com>
Reported-by: syzbot <syzbot+3ed715090790806d8b18@syzkaller.appspotmail.com>
Tested-by: syzbot <syzbot+43e93968b964e369db0b@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Fixes: 24b4b67d17 ("add ttyprintk driver")
Link: https://lore.kernel.org/r/17e0652d-89b7-c8c0-fb53-e7566ac9add4@i-love.sakura.ne.jp
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-04-22 12:01:26 +02:00
..
agp char/agp: Disable frontend without CONFIG_DRM_LEGACY 2020-11-18 22:47:45 +01:00
hw_random vio: make remove callback return void 2021-03-02 22:41:23 +11:00
ipmi ipmi: remove open coded version of SMBus block write 2021-01-28 07:15:12 -06:00
mwave char: mwave: remove unneeded break 2020-11-09 16:05:09 +01:00
pcmcia pcmcia: synclink_cs: drop redundant tty-port initialisation 2021-04-07 17:22:07 +02:00
tpm powerpc fixes for 5.12 #2 2021-03-07 13:24:44 -08:00
xilinx_hwicap treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
xillybus char: xillybus: use devm_platform_ioremap_resource() to simplify code 2019-11-05 18:29:21 +01:00
adi.c char: sparc64: Add privileged ADI driver 2018-06-05 11:24:55 -07:00
apm-emulation.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
applicom.c module: remove never implemented MODULE_SUPPORTED_DEVICE 2021-03-17 13:16:18 -07:00
applicom.h
bsr.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
ds1620.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
dsp56k.c vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
dtlk.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
hangcheck-timer.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 405 2019-06-05 17:37:13 +02:00
hpet.c char: hpet: Fix out-of-bounds read bug 2020-01-30 06:58:33 +01:00
Kconfig char: virtio: Select VIRTIO from VIRTIO_CONSOLE. 2020-09-07 14:32:40 +02:00
lp.c char: lp: remove unneeded break 2020-11-09 16:05:09 +01:00
Makefile rtc/alpha: remove legacy rtc driver 2020-03-19 07:41:02 +01:00
mem.c Fixes around VM_FPNMAP and follow_pfn 2021-02-22 17:45:02 -08:00
misc.c char: misc: increase DYNAMIC_MINORS value 2020-11-03 09:52:04 +01:00
mspec.c char: mspec: Use kvzalloc() in mspec_mmap() 2020-08-28 12:10:04 +02:00
nsc_gpio.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
nvram.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
nwbutton.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
nwbutton.h misc: cleanup minor number definitions in c file into miscdevice.h 2020-03-18 12:27:03 +01:00
nwflash.c misc: move FLASH_MINOR into miscdevice.h and fix conflicts 2020-03-18 12:27:04 +01:00
pc8736x_gpio.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
powernv-op-panel.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
ppdev.c ppdev: Distribute switch variables for initialization 2020-02-23 20:28:12 +01:00
ps3flash.c powerpc/ps3: make system bus's remove and shutdown callbacks return void 2020-12-04 01:01:22 +11:00
random.c Char/Misc driver patches for 5.12-rc1 2021-02-24 10:25:37 -08:00
raw.c raw: don't keep unopened block device around 2020-09-23 10:43:19 -06:00
scx200_gpio.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
sonypi.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 61 2019-05-24 17:36:45 +02:00
tb0219.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156 2019-05-30 11:26:35 -07:00
tlclk.c drivers: char: tlclk.c: Avoid data race between init and interrupt handler 2020-04-23 16:55:24 +02:00
toshiba.c module: remove never implemented MODULE_SUPPORTED_DEVICE 2021-03-17 13:16:18 -07:00
ttyprintk.c ttyprintk: Add TTY hangup callback. 2021-04-22 12:01:26 +02:00
uv_mmtimer.c
virtio_console.c virtio: virtio_console: fix DMA memory allocation for rproc serial 2020-11-09 18:03:33 +01:00